you need to catch it early, so when you click to shift and it doesn't respond is often indicative that one strand of cable has frayed inside the shifter. continue using it and the frayed strand frays more of the cable and then hey presto, click to shift and it snaps
next is about an hour of fannying around trying to pull the cable out
common shimano problem
you need to catch it early, so when you click to shift and it doesn't respond is often indicative that one strand of cable has frayed inside the shifter. continue using it and the frayed strand frays more of the cable and then hey presto, click to shift and it snaps
next is about an hour of fannying around trying to pull the cable out